Abstract: The basic function of public policy knowledge system is to explain the relation between policy and policy effectiveness. This paper argues that the construction of western public policy knowledge system is constrained by federalism, local decentralization and tenure system. It chooses “policy process” as the research object and “power structure” as the analysis unit to construct the knowledge system of policy stage theory and anti-stage theory, which is mainly used to understand and explain the reasons for the policy formation of a certain level of government or a department.Although this knowledge system has a good understanding and explanatory power, it can not fully understand and explain China’s policy practice. China is a unitary country. It implements the centralized system and cadre system, and has a complete policy system. Paying attention to the relations between policies and clarifying the policy relations have become the preconditions for China’s public policies to solve practical problems.Therefore, to understand and interpret China’s public policy, we need to take “policy relations” as the research object and “responsibility structure” as the analysis unit to construct a policy knowledge system with Chinese characteristics, which is also an important task of China’s public policy research.